Washington — If the top commander in Afghanistan asks for more US troops to accomplish the mission there, he will encounter a Pentagon that is reluctant to green-light the request.

Defense Secretary Robert Gates has said that Gen. Stanley McChrystal is free to ask for whatever he thinks is needed for the mission. But should the general ask for tens of thousands of more forces, as some analysts involved in his Afghanistan assessment have suggested, those troops may not be available right away.

Mr. Gates indicated as much Thursday when he said that providing more forces to Afghanistan in the near term would be a challenge because the drawdown in Iraq won't begin substantively until early next year.

"Until the more accelerated drawdown in Iraq begins after the elections there, it will be a challenge for us, and particularly as we seek to increase the dwell time at home for our forces," Gates said at a briefing at the Pentagon. "Dwell time" is the amount of time troops spend in the US between deployments. It gives the soldiers time with their families and helps ease the strain of long deployments.

Gates has made lengthening that time at home a priority as he manages demands in Iraq and Afghanistan. Asked if dwell time was more important than the mission in Afghanistan, Gates said, "I think you have to balance these things."

The defense secretary has authorized the Army to expand by 22,000 soldiers in order to have a big enough force during the drawdown in Iraq and the surge in Afghanistan. But that will take time, leaving a potential shortage in the short-term.

For now, no demand

General McChrystal's much-anticipated battlefield assessment, due next month, will not include a request for more forces, Gates confirmed Thursday. That request, should it come, will be separate. The significance of this is unclear, but it suggests that the administration is less focused on the number of troops it needs for Afghanistan than on the kinds of missions the troops need to perform.

Gates has already said that he fears too many troops in Afghanistan begin to resemble an occupation that will not be received well by an Afghan population that has endured more than 30 years of war. But he has also noted that the good conduct of US troops on the ground – something emphasized by McChrystal – can mitigate the impact of their presence.

By the end of fall, 68,000 American troops will be on the ground, including the 21,000 authorized by President Obama earlier this year. NATO has another 39,000 troops there.

A US brigade of about 5,500 troops is supposed to deploy to Afghanistan in late fall, Pentagon officials have pointed out, noting that it makes sense to wait to see what impact they have before deciding on more troops.

Playing down Afghanistan?

Still, more troops are inevitable, some experts say. The Pentagon runs the risk of undermining the mission there if it sends troops in a piecemeal fashion, they add, pointing to the success of the surge in Iraq, which quickly deployed as many as 30,000 troops over five months in early 2007.

As the Obama administration grapples with healthcare reform and the economy, some fear the needs of the mission in Afghanistan will be played down.

"I think they are worried about sticker shock," says an analyst who asked for anonymity because of his proximity to the matter. "No one has really explained to the American people how bad the situation is over there, and the administration has not focused on preparing people for this."

By contrast, the announcement in early 2007 of the surge of forces in Iraq telegraphed a clear message, the analyst said. "We told the enemy that you're going to have a brigade landing on your head very month."